As an alternative, the sword Umbra (part of the Clavicus Vile Daedric Quest), has a soul trap effect on strike, as do several other magical weapons. The longer the duration of the Soul Trap spell, the better, as you will have a longer time to capture the soul. You will need to have a Mysticism skill of at least 25 to use the most basic Soul Trap spell, although you can be of any level to use Soul Trap scrolls or a weapon with a Soul Trap enchantment on it.
